This two-part paper presents the results from modeling and optimization of alternative sustainable machining processes of Inconel 718. Nickel and Titanium, as representatives of high temperature alloys, with their specific thermo-mechanical properties, pose significant difficulties in machining. The high temperature and the consequent work hardening of these materials during the machining processes adversely affect cutting forces, tool-wear, surface integrity and chip breakability. This first part (Part 1) of the paper presents the experimental study of sustainable high performance machining of Inconel 718 with the development of performance-based predictive models for dry, near-dry (MQL), cryogenic and cryo-lubrication (cryogenic + near-dry) machining processes using response surface methodology (RSM).
COBISS.SI-ID: 13552667
This paper presents the influence of the nitrogen fluid phase on the surface heat transfer coefficient in cryogenic machining. A novel optical nitrogen phase sensor was developed for characterizing the cryogenic fluid phase. Surface heat transfer coefficients were established experimentally by using a new heat transfer model for cryogenic machining. A finite element model was developed utilizing experimental data for Inconel 718. Using it, the process behavior with varying nitrogen phases was simulated. Determining the minimal, but sufficient amount of coolant flow-rate, in combination with the desired fluid phase at the delivery, was found to be the key for achieving truly sustainable cryogenic machining.
COBISS.SI-ID: 14521883
Global competition, stricter environmental legislation and demands for fulfilling sustainability initiatives, are increasing the pressure on the manufacturing industry, to develop and implement in their production alternative sustainable machining processes. This work focuses on sustainability evaluation and comparison in machining of high-temperature Nickel-based alloy (Inconel 718). Four sustainable machining alternatives (dry, near-dry (MQL), cryogenic and cryo-lubrication (cryogenic + near-dry)) to conventional machining, are evaluated based on the performance models from the Part 1 of the paper and used in the optimization procedure for determining the overall optimum machining conditions. As chip breakability is important machining characteristic, performance-based models of sustainable machining processes, developed in Part 1, are upgraded in this Part 2 of the paper with an additional model for chip breakability.
COBISS.SI-ID: 13790491
The paper analyses the influence of emulsion mist formation parameters and the nozzle distance from the tool%chip interface, on the droplet velocity at the nozzle outlet, on active medium atomization angle as well as on the diameter and number of droplets supplied to the cutting zone. The deformation coefficient of the droplets falling on the surface and the wetting angle have also been determined. In the work it has been proved that the strongest influence on the droplets diameter have the air flow and the distance of the nozzle from the cutting zone. It has been shown that larger angle of the stream splitting ensures that the droplets do not join each other in the air, and consequently assures small diameter on the surface. Additionally, the results show that the emulsion mass flow does not change the droplets diameters by more than 12%. It has been determined that smaller the droplets diameter is, higher content of active compounds in the tribofilms formed on the machined surface is present. In this way the paper presents the analysis and directions of MQCL adjustment trends needed to improve the machining performance.
COBISS.SI-ID: 14281243
Cryogenically assisted manufacturing processes are emerging as environmentally-benign, toxic-free, hazardless operations, producing functionally superior products. This paper presents an overview of major cryogenic manufacturing processes, summarizing the state-of-the-art and significant developments during the last few decades. It begins with a summary of historic perspectives, including definitions, scope, and proceeds to analysis of process mechanics and material performance covering tribological and thermo-mechanical interactions, followed by surface integrity, product quality and performance in cryogenic manufacturing. Process analysis and applications includes machining, forming and grinding. Economic, safety and health issues are then discussed. Finally, progress in developing predictive performance models and future outlook are presented.
COBISS.SI-ID: 14829851